MongoDb 在子字段中查找字符串

Question

Let's say we have a collection that has elements that look like this:

{
"_id" : ObjectId(...),
"field1": "some_text",
"field2": {
                "subfield1" : [
                        "some_text",
                        "some_text",
                        "some_text"
                ],
                "subfield2" : [
                        "some_text",
                        "some_text"
                ],
                "subfield3" : [
                        "some_text"
                ]
        }
}

Now what I want to do is, I want to find all the ids that have a certain string inside the field2 value. Doesn't matter in which subfield. If there is such string there, I want that whole element to be returned. Imagine that there are 100 subfields. I don't want to check each of them separately.

How would this be done?

Answer 1

Use this to put all values into one single array. Then it is easy to find a particular string in subfields array.

db.collection.aggregate([
  {
    $set: {
      subfields: { $objectToArray: [ "$field2" ] }
    }
  },
  {
    $set: {
      subfields: {
        $reduce: {
          input: { $concatArrays: [ "$subfields.v" ] },
          initialValue: [],
          in: { $concatArrays: [ "$$value", "$$this" ] }
        }
      }
    }
  },
  {$match: {subfields: "whatever you are looking for"}},
  {$unset: "subfields"}
])